This actor calculates the Fast Fourier Transform of a sequence of
complex inputs. The order of the FFT determines the number of tokens
that will be consumed and produced on each firing. The order is the
base-2 logarithm of the size. The default order is 8, which means that
28 = 256 tokens are read and 28 = 256 tokens are
produced. The result of the FFT is a new array of Complex tokens.